Only in the rarest cases are microscopic samples investigated directly and without further processing in a light microscope or even an electron microscope. Most microscopy inquiries and specimens require more or less comprehensive preparation.
Material to be examined microscopically is usually fixed and embedded. Sample sections can be produced from the embedded material, for example using a microtome. These can be stained and, after placement onto a specimen slide, visually investigated and/or digitized. An overview of corresponding techniques is provided, for example, by Mulisch, M. and Welsch, U. (eds.): Romeis-Mikroskopische Technik [Microscopy technique], 10th ed., Heidelberg: Spektrum Akademischer Verlag, 2010.
Microscopes are generally used to detect small structures not detectable with the naked eye, and to locate characteristic features in such structures. A basic microscopy task in cytology, histology, and pathology is to scan a prepared specimen and examine it for structures, cells, cell groups, and the like that are of interest. Once the locations of such structures on the prepared specimen have been found, it is desirable for many reasons to remember them. For example, a structure must be located again at a later point in time by the same or another user for purposes of checking or further inspection, or for quality assurance reasons.
Many microscopes have for this purpose a unit for ascertaining the coordinates of positions of a point in a device-dependent coordinate system. The position that has been located can be traveled to later by ascertaining those coordinates electromechanically
The coordinates are conventionally device-dependent, i.e. the coordinates can be exactly reproduced for that device only if no changes have been made in microscope alignment and if no tolerances exist. If, however, the microscope stage has been removed for repair and reattached, for example, it may possibly furnish for the same location on the prepared specimen coordinates different from those originally determined The coordinate systems of different microscopes, even those of the same model or the same series, are also not (exactly) identical.
This is even more relevant if the corresponding coordinates are to be reproduced not in a microscope but in a sample processing device such as, for example, a (laser) microdissection unit, or if the coordinates are determined not in a microscope but rather, for example, in a slide scanner. The more different the configuration of the respective devices involved, the more complex an interchange generally turns out to be.
DE 103 36 803 A1 discloses a method and a system for device-independent determination of coordinates of a point imaged by means of a microscope. Provision is made here that firstly, for predetermined specimen-related reference coordinates of at least one reference point in a DICOM (Digital Imaging and COmmunications in Medicine) coordinate system, the associated device coordinates of the at least one imaged reference point are determined in a device-dependent coordinate system, and a transformation rule for converting device-dependent coordinates into the coordinates of the DICOM coordinate system is identified. The device coordinates of the imaged point can then be converted, by means of the transformation rule that has been discovered, into device-independent coordinates of the DICOM coordinate system.
This method and system prove to be complex in practice, however, since all the devices involved must each be set up to carry out the necessary steps and must possess corresponding calculation units, e.g. for ascertaining the transformation rule.
A need therefore continues to exist for, in particular, simplified capabilities for determining and/or retrieving a position on a specimen slide, in particular in a sample investigation system made up of the different components explained above.